Patterned nanoparticle structures

ABSTRACT

Aspects relate to patterned nanostructures having a feature size not including film thickness of below 5 microns. The patterned nanostructures are made up of nanoparticles having an average particle size of less than 100 nm. A nanoparticle composition, which, in some cases, includes a binder, is applied to a substrate. A patterned mold used in concert with electromagnetic radiation function to manipulate the nanoparticle composition in forming the patterned nanostructure. In some embodiments, the patterned mold nanoimprints a pattern onto the nanoparticle composition and the composition is cured through UV or thermal energy, Three-dimensional patterned nanostructures may be formed. A number of patterned nanostructure layers may be prepared and joined together. In some cases, a patterned nanostructure may be formed as a layer that is releasable from the substrate upon which it is initially formed. Such releasable layers may be arranged to form a three-dimensional patterned nanostructure for suitable applications.

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. application Ser. No.13/900,248, filed May 22, 2013, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Application No. 61/650,214, filed May 22,2012, each of which is incorporated herein by reference in its entirety.

FEDERALLY SPONSORED RESEARCH

This invention was made with government support under contract numberCMMI-1025020 awarded by the National Science Foundation. The governmenthas certain rights in the invention.

FIELD OF INVENTION

Aspects described herein relate generally to patterned nanostructurescomprising nanoparticles.

BACKGROUND

Devices having improved optical and electronic properties have gainedincreasing interest, particularly at the sub-micron length scale. Suchdevices may be composed of inorganic materials such as metals, metaloxides, semiconductors (e.g., silicon), carbonaceous or other amorphous,crystalline and/or semi-crystalline compositions. Traditionalmanufacturing techniques for semiconductors having certainopto-electronic properties involve subtractive processes where materialis built up and removed through various mask/etch processes. The typesof materials that are involved using these techniques are limited.Further, such subtractive processes can be expensive and wasteful.

Direct write techniques have been used as an additive process to producepatterns of metal oxides and other materials by precipitation andcoagulation of inks dispensed from nozzles of parallel ink heads. Thistechnique, however, has a number of disadvantages by being slow, limitedto large micron scale dimensions, unable to be used to manipulatesemi-crystalline, crystalline or conducting compositions at lowtemperature, and is not easily scalable.

Accordingly, improved additive techniques for forming patternedstructures having dimensions at sub-micron lengths through high-speedmanufacturing processes would provide advantages to the current state ofthe art.

SUMMARY

Patterned nanoparticle structures suitable for various applications, andrelated components, systems, and methods associated therewith areprovided.

In an illustrative embodiment, a material is provided. The materialcomprises a plurality of nanoparticles formed as a patternednanostructure having a feature size not including film thickness ofbelow 5 microns, wherein the plurality of nanoparticles have an averageparticle size of less than 100 nm.

In another illustrative embodiment, a method of forming a patternednanostructure is provided. The method includes applying a nanoparticlecomposition to a surface of a substrate, the nanoparticle compositionincluding a plurality of nanoparticles having an average particle sizeof less than 100 nm; and using electromagnetic radiation in cooperationwith a patterned mold and/or mask to manipulate the nanoparticlecomposition and form the patterned nanostructure, wherein the patternednanostructure has a feature size not including film thickness of below 5microns.

In a further illustrative embodiment, a method of forming athree-dimensional patterned nanostructure is provided. The methodincludes forming a first patterned nanostructure layer having a firstfeature size not including film thickness below 5 microns, the firstpatterned nanostructure layer including a first plurality ofnanoparticles having an average particle size of less than 100 nm. Themethod also includes forming a second patterned nanostructure layerhaving a second feature size not including film thickness below 5microns, the second patterned nanostructure layer including a secondplurality of nanoparticles having an average particle size of less than100 nm; and placing the second patterned nanostructure layer over thefirst patterned nanostructure layer.

The foregoing is a non-limiting summary of the invention, which isdefined by the attached claims. Other aspects, embodiments, features andadvantages will become apparent from the following description. Eachreference incorporated herein by reference is incorporated in itsentirety. In cases of conflict or inconsistency between an incorporatedreference and the present specification, the present specification willcontrol.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are not intended to be drawn to scale. Forpurposes of clarity, not every component may be labeled in everydrawing. In the drawings:

FIG. 1A shows processing steps for ultraviolet-assisted nanoimprintlithography;

FIG. 1B shows processing steps for thermal nanoimprint lithography;

FIG. 1C shows a schematic for ultraviolet-assisted nanoimprintlithography;

FIGS. 2A-2F illustrate atomic force microscope (AFM) images of patternednanoparticle structures having a line pattern in accordance with someexamples;

FIG. 3 depicts scanning electron microscope (SEM) images of otherpatterned nanoparticle structures having a line pattern in accordancewith some examples;

FIG. 4 shows SEM images of patterned nanoparticle structures having aline pattern with triangular shaped cross-sections in accordance withsome examples;

FIG. 5 shows SEM images of patterned nanoparticle structures havingrectangular shapes in accordance with some examples;

FIG. 6 illustrates SEM images of patterned nanoparticle structureshaving circular shapes in accordance with some examples;

FIG. 7 depicts SEM images of patterned nanoparticle structures having aline pattern in accordance with some examples;

FIG. 8 illustrates SEM images of further patterned nanoparticlestructures having a line pattern in accordance with some examples;

FIG. 9 shows SEM images of patterned nanoparticle structures having aline pattern in accordance with some examples;

FIG. 10 depicts a graph of percent loss in thickness as a function ofnanoparticle weight and volume percentage at various calcinationtemperatures;

FIG. 11 shows SEM images of patterned nanoparticle structures having aline pattern in accordance with some examples;

FIG. 12 illustrates SEM images of patterned nanoparticle structureshaving a line pattern in accordance with some examples;

FIG. 13 depicts X-ray diffraction results of patterned nanoparticlestructures in accordance with some examples;

FIG. 14 shows X-ray diffraction results of patterned nanoparticlestructures accordance with some examples;

FIGS. 15A-15F depict AFM images of patterned nanoparticle structureshaving a line pattern in accordance with some examples;

FIGS. 16A-16F show AFM images of patterned nanoparticle structureshaving a line to pattern in accordance with some examples;

FIG. 17 shows SEM images of three-dimensional patterned nanoparticlestructures in accordance with some examples;

FIG. 18 depicts SEM images of three-dimensional patterned nanoparticlestructures in accordance with some examples;

FIG. 19 shows a graph of reflectance as a function of wavelength ofthree-dimensional patterned nanoparticle structures in accordance withsome examples;

FIG. 20 depicts a graph of refractive index as a function of wavelengthof patterned nanoparticle structures in accordance with some examples;

FIG. 21 illustrates a graph of percent transmittance as a function ofwavelength of patterned nanoparticle structures in accordance with someexamples;

FIG. 22 shows X-ray diffraction results of patterned nanoparticlestructures in accordance with some examples;

FIG. 23 depicts FT-IR spectra of patterned nanoparticle structures inaccordance with some examples;

FIG. 24 illustrates photo-DSC thermograms of patterned nanoparticlestructures in accordance with some examples;

FIG. 25 depicts measures of adhesion of patterned nanoparticlestructures in accordance with some examples;

FIG. 26 shows chemical structures for a component of a patternednanoparticle structure in accordance with some examples;

FIG. 27 illustrates a crosslinking mechanism involved in preparing apatterned nanoparticle structure in accordance with some examples;

FIG. 28 shows a table indicating the roughness of the planar films as afunction of nanoparticle loading in accordance with some examples;

FIG. 29 shows cross sectional SEM images of high aspect ratio patternednanoparticle structures having a line pattern in accordance with someexamples;

FIG. 30 depicts cross sectional SEM images of high aspect ratiopatterned nanoparticle structures having a line pattern in accordancewith some examples;

FIG. 31 shows cross sectional SEM images of high aspect ratio patternednanoparticle structures having a line pattern in accordance with someexamples; and

FIG. 32 illustrates cross sectional SEM images of high aspect ratiopatterned nanoparticle structures having a line pattern in accordancewith some examples.

DETAILED DESCRIPTION

The present disclosure relates to patterned nanostructures having aplurality of nanoparticles where the patterned nanostructure has afeature size that is below 5 microns (e.g., below 3 microns, below 1micron, below 500 nm). As determined herein, a feature size of apatterned nanostructure is considered to be a designed dimension havingresulted from a patterning fabrication process of a nanoparticlecomposition other than the film thickness of the nanostructure itself orother incidental surface asperities. In some cases, the feature size isconsidered to be a critical dimension of the patterned nanostructure.Some examples of feature sizes include, but are not limited to, a widthof patterned lines (straight or curved), a frequency of periodicstructures, a distance between edges of a geometric structure, etc. Insome embodiments, the plurality of nanoparticles of the patternednanostructure may have an average particle size of less than 100 nm.

Methods are described that involve direct, additive fabrication of metaloxide (e.g., amorphous, crystalline, semi-crystalline), metal andsemiconductor nanostructures via patterning compositions ofnanoparticles. Such methods may employ any suitable type ofelectromagnetic radiation, such as ultraviolet (UV), near-IR, thermal,visible, infrared or any other appropriate radiation. Forming apatterned nanostructure having a feature size of below 5 microns mayinvolve applying a nanoparticle composition to a surface of a substrate.Electromagnetic radiation is used in cooperation with a patterned moldto manipulate the nanoparticle composition and form the patternednanostructure. For instance, using nanoimprint lithography (NIL), apatterned mold may be appropriately placed into contact (e.g., pressed)with the nanoparticle composition having been applied to the surface ofthe substrate resulting in a nanoparticle composition having a patternthat conforms to the shape of the patterned mold. The nanoparticlecomposition may then be cured or crystallized, for example, throughcrosslinking of various components of the composition from exposure to asuitable energy source, such as heat or ultraviolet radiation. Othertechniques may be used, such as nanoinscribing, photolithography,capillary force lithography and/or electron beam lithography.

Aspects of the present disclosure provide for crystalline nanostructureddevices comprising metal oxide nanoparticles to be fabricated via anadditive process that has a number of advantages.

One advantage of nanostructured devices described herein is that suchdevices may be tuned to exhibit particular optoelectronic properties(e.g., refractive index, transmittance, reflectance, etc.) based oncertain aspects of how they are fabricated, such as the particularpercent combination of materials, type of materials incorporated, etc.

Another advantage is that nanostructured devices may be fabricated so asto exhibit a relatively small amount of volume contraction uponcalcination. In certain methods of fabrication, metal oxides to beprocessed into a nanostructured device are initially provided in acomposition that has a substantial amorphous state. When suchcompositions are subject to a step of calcination (for crystallizationof the overall composition), there is a tendency for the volume of thecomposition to shrink substantially, which may be disruptive to thegeneral structure of the material. However, in accordance withembodiments of the present disclosure, metal oxide nanoparticles thatare highly crystalline (e.g., 90-95% crystalline) are initiallyprovided. A sol-gel precursor is used as a binder (e.g., rather than apolymer binder) together with the metal oxide nanoparticles to form ananostructure composition. The nanostructure composition including themetal oxide nanoparticles and sol-gel precursor is then subject tocalcination, which causes the amorphous portion of the composition toshrink. However, because the composition is predominantly crystalline inits initial state (metal oxide nanoparticles and sol-gel precursorcombination), the composition is subject to minimal shrinkage, such asthat shown in the Example provided in FIG. 10.

For instance, in some embodiments, the percent reduction in thicknessupon calcination of a nanostructured layer, fabricated in accordancewith embodiments described herein, may be less than 50% (e.g., less than40%, less than 35%, less than 30%, less than 25%, less than 20%, lessthan 15%, less than 10%) for compositions where metal oxidenanoparticles are initially provided at a weight percentage of greaterthan 20% (e.g., greater than 30%, greater than 35%, greater than 40%,greater than 50%, greater than 60%, greater than 70%, greater than 80%,greater than 90%, greater than 95%). It is believed that because thesol-gel precursor already has crystalline properties along with themetal oxide, upon calcination, there is an overall reduction inshrinkage of the nanoparticle composition that would otherwise occur.

Patterned nanostructures described herein may be made into athree-dimensional (3D) patterned structure having one or more featureseach having a characteristic feature size (e.g., width, spacing,diameter, radius, ridge dimension, pitch, etc.). For example, a firstpatterned nanostructure layer having a first feature size below 5microns may be formed separately, or in combination with, a secondpatterned nanostructure layer having a second feature size below 5microns. The second patterned nanostructure layer may be placed over thefirst patterned nanostructure layer. Both the first and second patternednanostructure layers may include nanoparticles haying an averageparticle size of less than 100 nm. Any suitable number of patternednanostructure layers may be formed and incorporated into a stack ofpatterned nanostructure layers where each layer has its own pattern. Insome embodiments, a patterned nanostructure layer may be prepared in amanner so as to be releasable from the substrate upon which it wasformed. For example, an intermediate layer may be employed between thesubstrate and the nanoparticle composition. Accordingly, the patternednanostructure layer may be joined with other layers so as to form a 3Dnanostructure.

In some embodiments, UV-assisted NIL is employed. UV-assisted NIL mayconfer a number of advantages, such as low temperature fabrication ofpredominantly crystalline structures, the ability to directly patternstructures having a feature size as small as the dimension of thenanoparticle being patterned, the ability to rapidly pattern large areasin a scalable manner, the ability to stack patterned structures to form3D nanostructured composites, and others.

The present disclosure describes compositions and methods for patterningnanocomposite films or coatings containing nanoparticles and UV curable,thermally curable and/or chemically cross-linked materials to generatepatterned nanostructures. Various compositions including a variety ofnanoparticles and curable materials are discussed herein and may besuccessfully patterned into nanostructures with sub-500 nm feature sizeand larger dimensions through the use of nanoimprint lithography,nanoinscribing lithography, photolithography or variants of thesetechniques. These compositions can be either aqueous or organic solventbased, which allows for the solvent to be chosen based on the desiredapplication. Nanoparticles contemplated to be incorporated for use informing patterned nanostructures include metal oxides, mixed metaloxides, metals, and/or other suitable materials, or combinationsthereof.

In an embodiment, nanoparticles are free of covalently bound ligands.For example, the nanoparticles are non-functionalized. The nanoparticlescan be dielectric, semiconducting or conducting. The nanostructures canbe comprised of one or more compositions of nanoparticles and one ormore sizes of nanoparticles. The coating solution that includes thenanoparticle composition may contain dopants, functional additives,functional polymers, metal oxide precursors or sols, or organics thatpersist throughout or on the structure.

In some embodiments, layers containing the patterned nanoparticles canbe stacked in any suitable manner. For instance, free standing patternednanostructures can be released from a support structure as patternednanostructure layers, and the patterned nanostructure layers may, inturn, be stacked to create 3D nanostructures. An advantage of thisapproach, relative to the current state of the art, is the ability tocreate nanostructures having sub-wavelength dimensions, which allow forcontrolled manipulation of various wavelengths of light andelectromagnetic waves.

Nanoparticles having dimensions (e.g., width, diameter, etc.) less than100 nm may exhibit similar or different properties from those of thebulk material. As dimensions become quite small, the properties of thenanoparticles can be size dependent. For instance, small nanoparticlescan exhibit a number of interesting properties, such as catalytic,magnetic, mechanical, electrical and optical properties, that are eithernot observed in their bulk material counterparts or exhibit enhancementwhen isolated as a nanoparticle. To take advantage of the properties ofnanoparticles, nanocomposite materials may be developed to incorporatenanoparticles into various host matrices such as polymers, blockcopolymers and metal oxides. In some embodiments, the plurality ofnanoparticles of a nanoparticle composition may have an average particlesize (e.g., width, diameter) of less than 100 nm, less than 90 nm, lessthan 80 nm, less than 70 nm, less than 60 nm, less than 50 nm, less than40 nm, less than 30 nm, less than 20 nm, less than 10 nm, less than 5nm, or less than 2 nm.

Using methods described herein (e.g., NIL, NIS, photolithography), thepatterned nanostructure comprising the nanoparticle composition has afeature size of less than 5 microns, less than 4 microns, less than 3microns, less than 2 microns, less than 1 micron, less than 500 nm, lessthan 300 nm, less than 100 nm, less than 50 nm, or less than 20 nm. Forinstance, nanoparticle compositions may have features that are columnarin cross section (e.g., according to a master mold having a particularline width, depth and pitch). Such features may have a width or heightof 10-1000 nm, 50-500 nm, 100-300 nm, and/or may also exhibit a highaspect ratio, for example, 2:1, 2.5:1, 3:1, 3,5:1, 4:1, 4.5:1, 5:1, 6:1,7:1:, 8:1, 9:1, 10:1. or higher. It can be appreciated that thepatterned nanostructure may include any suitable shape or geometricconfiguration, such as columns, rows, striped, complex/irregular shapes,arcuate or polygonal patterns and having appropriate dimensions.

Nanoparticle compositions may include a binder material that can bederived, for example, from any suitable curable monomers, oligomers,polymers, metal oxide precursors, metal oxide sols, sol-gel precursorsand/or other reactive or crosslinkable media. Nanoparticles may be incontact with the binder material. For example, the binder material maybe located between nanoparticles such that a majority of thenanoparticles are separated by the binder material. Depending on thepreferred characteristics of the patterned nanostructure, the bindermaterial may be an insulative or a conductive material.

In some embodiments, nanoparticle compositions can be processed usingphotolithography to induce regioselective reaction of the nanoparticlesor the binder material such that certain regions of the composition canbe removed by subsequent steps including photolithographic developmentin water or other solvent. In some embodiments, combinations ofphotolithography and imprint lithography can be employed. In someembodiments, reactive media can be provided as functional groups on thenanoparticles or as ligands bound to the nanoparticles. The nanoparticlecomposition may include dopants, surface modifiers, fullerenes or otherfunctional materials that influence the behavior and characteristics ofthe nanostructures.

To incorporate nanoparticles into polymers, two general approaches maybe considered—in-situ formation of nanoparticles with polymers; and/orblending crystalline nanoparticles with polymers. The fabrication ofcomposites from in-situ formation of nanoparticles can be accomplishedby physical or chemical methods. The use of in-situ reactions may ofteninvolve harsh processing conditions and/or involve post-compositeformation processing steps to generate a desired nanoparticle.

Nanoparticle compositions may be prepared from pre-synthesizednanoparticles and, in some cases, may remove a number of disadvantagesassociated with in-situ nanoparticle generation. For example, synthesisof the nanoparticle may be performed in a separate reaction prior toincorporation into the overall system. The separation of nanoparticleformation from composition formation may allow for the nanoparticle toretain advantageous properties, such as crystallinity, withoutperforming additional post-composition formation steps, such ascrystallization procedures of either high-temperature or hydrothermaltreatments.

In taking advantage of various properties afforded to nanoparticlecompositions (e.g., nanoparticle polymer composites), such asconductivity and refractive index characteristics, the compositions maybe patterned in particular areas and geometries. NIL offers thecapability of providing nanometer resolution, large area patterning andfavorable throughput. Two general methods of imprint lithography may beused to produce nanoscale features—Thermal nanoimprint lithography(TNIL) and ultraviolet-assisted nanoimprint lithography (UV-NIL).

Nanoimprint lithography, generally, is a method of fabricating nanometerscale patterns at low cost, high throughput and high resolution. NILcreates patterns by using a mold to mechanically deform a softer imprintresist (e.g., a nanoparticle composition coated on to the surface of asubstrate) and exposing the imprint resist to subsequent processes(e.g., heat/UV curing). It can be appreciated that molds may exhibitcharacteristics that are comprised of but not limited to rigid orflexible characteristics. While TNIL and UV-NIL are suitable methods forpatterning a nanoparticle composition, other methods may be used, inaddition to methods other than imprint lithography.

As shown in FIG. 1A, in UV-NIL, for some embodiments, aphotocrosslinkable resin (e.g., a nanoparticle composition) is formed onor applied to a surface of a substrate. A transparent mold is broughtinto contact with the photocrosslinkable resin, mechanically deformingthe resin so as to conform to the shape of the mold. While the mold ismaintained on the photocrosslinkable resin, the resin is exposed to UVradiation resulting in the resin being crosslinked. After the resin iscrosslinked, the mold is removed, leaving the resin having anappropriately patterned structure.

FIG. 1B illustrates an example of thermal nanoimprint lithography, whichis similar to UV-NIL except that heat is used to cure the resin (e.g., ananoparticle composition) rather than UV radiation. As shown in theexample, a thermal (curable) composition is formed on a substrate. Anappropriate mold having a suitable pattern is brought into contact withthe thermal (curable) composition and the composition is heat cured.

FIG. 1C shows a schematic of an example process for patterning ananoparticle composite using solvent assisted UV-NIL. Here, ananoparticle composition is spin coated as a photoresist on to asubstrate. A transparent mold is placed over and on to the nanoparticlecomposition. When the mold is firmly situated so that the nanoparticlecomposition conforms to the shape of the mold, the system is irradiatedwith UV light allowing for the nanoparticle composition to cure. Oncethe nanoparticle composition is fully cured, the mold is removed, andthe patterned nanoparticle composition remains for further processingand use.

In some embodiments, nanoparticle compositions are manipulated to form apatterned nanostructure by exposing the nanoparticle composition to atemperature of less than 200 C, less than 150 C, less than 100 C, lessthan 50 C, or room temperature. In some embodiments, in forming thepatterned nanostructure, the nanoparticle composition is exposed to atemperature no greater than room temperature, no greater than 30 C, nogreater than 40 C, no greater than 50 C, no greater than 100 C, nogreater than 150 C, no greater than 200 C, no greater than 250 C, nogreater than 300 C, no greater than 350 C and no greater than furthertemperatures in 50 C increments up to 2000 C. For example, a patternednanostructure may be formed from nanoparticles without a step ofannealing or sintering of the nanoparticles.

Alternatively, nanoinscribing (NIS) lithography may be used, whichrelies on site-specific plastic deformation of the underlyingcomposition (e.g., at slightly elevated pressures) through contact witha relatively stiffer mold to yield the patterned nanostructure. In somecases, nanoinscribing involves a mold having an appropriate pattern ofchannels that are dragged through the nanoparticle composition so as toform a suitable pattern in the composition itself. The nanoparticlecomposition with the pattern inscribed therein is then appropriatelycured. NIS provides the ability to pattern continuous nanostructures ofthin films of metals, metal oxides, and/or functional polymers at roomtemperature or elevated temperatures via localized heating, In someembodiments, NIS, NIL or any other suitable technique may be used togenerate patterned nanostructures, which may have feature sizes smallerthan 500 nm, in nanostructures including, for example, metal oxide,mixed metal oxide, carbonaceous nanoparticles including fullerenes andgraphene, metal nanoparticles, and/or combinations thereof.

Photolithography may also be used where, essentially, a portion of thenanoparticle composition is removed so as to form the patternednanostructure. Photolithography is a subtractive process where, in someembodiments, a photoresist is applied over the nanoparticle compositioncoated on the substrate and a mask is applied over the photoresist. Thesystem is then exposed to an appropriate amount of radiation (e.g., UVlight) distributed toward the photoresist according to the mask patternand the portion of the photoresist that is exposed to the radiation isremoved. Through an appropriate etching and removal process, thenanoparticle composition is then suitably patterned. In someembodiments, using photolithography to fabricate the patternednanostructures may involve the nanoparticle composition itself beingused as a photoresist.

In some embodiments, during curing and/or crystallization, thenanoparticle composition is selectively heated due to exposure toradiation originating from an optical pulse source. For instance, thesurface of the nanoparticle composition may be selectively heated (e.g.,between 800-900 C) without substantial heating occurring to the bulk ofthe composition. Such selective heating may be useful when fabricatingcrystalline nanoparticle films on a substrate where it may beundesirable to expose the underlying substrate to excessive heat (e.g.,a flexible polymeric substrate).

Selective heating may occur may any suitable method. In someembodiments, surface selective heating may occur through short,high-energy pulses, such as those that arise from an optical pulsedflash lamp (e.g., Xenon emission source) that emits radiation rangingfrom ultraviolet to near-infrared wavelengths. The flash sequence of thepulsed source may be tuned so as to adjust the amount of heat and thedegree of penetration to which the nanoparticle composition is exposed.A generalized approach is provided for patterning a diverse array ofnanoparticle and nanoparticle compositions (e.g., single or compositecompositions) which may include, for example, crystalline metal oxidenanoparticles, mixed metal oxide nanoparticles and metal oxidenanoparticles/metal oxide precursor compositions. Such nanoparticlecompositions may exhibit favorable properties, such as good mechanicalintegrity, high optical transparency, tunable refractive indices, goodelectrical conductivity, good thermal conductivity, and others. In someembodiments, the nanoparticles may be amorphous. In some embodiments,the nanoparticles can be metals, semiconductors or carbonaceouscompositions including fullerenes, graphene, and graphene oxides. Suchnanoparticle compositions are capable of being patterned by UV-NIL, NIS,or any other suitable technique.

Nanoparticle compositions (e.g., nanoparticle polymer composites) forpatterning via UV-NIL may be aqueous or non-aqueous based. In someembodiments, nanoparticle compositions include nanoparticles mixed witha binder material. For example, nanoparticle compositions may comprisewater and/or a polar aprotic diluent and a polar protic diluent, acolloidal inorganic oxide, and/or an inorganic precursor, and/or athermally curable, and/or UV curable, and/or chemically crosslinkablephotoresist.

Nanoparticles may initially be obtained as a solution with apredominantly aqueous solvent (e.g., greater than 90% by weight water).Though, the high degree of polarity of the water may give rise to asurface tension that may interfere with the quality of formation of thepatterned nanostructure (e.g., the patterned nanostructures are stillable to form, but not as precisely when the surface tension of thesolvent is so high). Accordingly, in some embodiments, the initialnanoparticle composition may be subject to a solvent exchange where thewater is essentially replaced with a different solvent (e.g., alcohol,organic solvent, etc.) that exhibits a less degree of polarity thanwater, reducing the surface tension of the overall composition. Forexample, preparing the nanoparticle composition may involve exchanging afirst aqueous solvent comprising greater than 90% by weight water with asecond generally non-aqueous solvent comprising less than 10% by weightwater. A small amount of water may still be present after solventexchange has occurred.

Such a non-aqueous solvent may include any suitable combination of anaprotic solvent (e.g., N-methyl pyrrolidone, dimethyl sulfoxide,dimethylformamide, dioxane and hexamethylphosphorotriamide,tetrahydrofuran), a protic solvent (e.g., alcohols, methanol, ethanol,formic acid, ammonia, etc.), or any other suitable solvent whichexhibits less polarity than water. Aprotic solvents are solvents thatare able to dissolve ions, yet, for the most part, lack an acidichydrogen or a labile proton. Aprotic solvents generally do not undergohydrogen bonding and are able to stabilize ions. Protic solvents aresolvents that have a hydrogen atom hound to an oxygen (e.g., hydroxylgroup) or a nitrogen (e.g., amine group) and are able to dissociate anddonate a proton. Protic solvents generally undergo hydrogen bonding andare able to stabilize ions.

In some embodiments, patterned nanostructures may include nanoparticles,crosslinked nanoparticles, and nanoparticle composite systems. In someembodiments, patterned nanostructures may be formed from metal oxide andmixed metal oxide systems with nanoparticle composite systems rangingfrom 10 wt. % to 100 wt. % with a binder material such as a UV curablemonomer, sol-gel precursor, and/or prepolymer material that is capableof undergoing UV-NIL.

The concentration of nanoparticles in the nanoparticle composition canvary by any suitable amount. For example, the nanoparticles may comprisegreater than or equal to 50% by weight, greater than or equal to 60% byweight, greater than or equal to 70% by weight, greater than or equal to80% by weight, greater than or equal to 90% by weight, or 100% by weightof the patterned nanostructure or of the nanoparticle composition. Thenanoparticles may also comprise less than or equal to 50% by weight, ofthe patterned nanostructure or of the nanoparticle composition. Theconcentration of binder material in the nanoparticle composition mayvary appropriately. In some embodiments, the binder material maycomprise less than or equal to 50% by weight, less than or equal to 40%by weight, less than or equal to 30% by weight, less than or equal to20% by weight, less than or equal to 10% by weight, or 0% by weight ofthe patterned nanostructure or of the nanoparticle composition. Thebinder material may also comprise greater than or equal to 50% byweight, of the patterned nanostructure or of the nanoparticlecomposition.

In some embodiments, the binder material of the nanoparticle compositionmay include an optical adhesive material. An optical adhesive may betransparent or translucent. In some cases, when an optical adhesive isexposed to UV light, the material cures (e.g., crosslinks). The relativeconcentration of nanoparticle and optical adhesive material, the type ofnanoparticle, and the porosity of the nanoparticle composition mayultimately affect the refractive index of the patterned nanostructure.For example, when the nanoparticle concentration of the nanoparticlecomposition is greater, the refractive index of the patternednanostructure may also be greater. Accordingly, the refractive index ofpatterned nanostructures comprising nanoparticles described herein maybe suitably tuned. In some embodiments, the refractive index ofpatterned nanostructures may range between about 1.0 and about 5.0,between about 1.0 and about 3.0, between about 1.0 and about 1.5,between about 1.1 and about 1.7, or between 1.5 and 2.5. Opticaladhesive materials may be insulative, semi-conductive or conductive innature.

Patterned nanostructures may be fabricated as three-dimensionalpatterned nanostructures, for example, provided as layers in a stackedarrangement. In some embodiments, such a stacked arrangement may includemultiple patterned nanostructure layers where each of the patternednanostructure layers has a particular refractive index. The refractiveindex of each of the patterned nanostructure layers may be tuned inaccordance with embodiments described herein, for example, based on theoverall composition (e.g., relative weight/volume percentage ofingredients) of the layer.

In some embodiments, patterned nanostructure layers of athree-dimensional stack may have refractive indices such that thestacked nanostructure exhibits a gradient of refractive indices. Forexample, one end of a three-dimensional stack of patterned nanostructurelayers may exhibit a relatively low refractive index (e.g., 1.1-1.5) andan opposing end of the three-dimensional stack may exhibit a relativelyhigh refractive index (e.g., 1.5-4.0, 1.5-2.0, 2.0-3.0). Accordingly,patterned nanostructure layers positioned in between the opposing endsmay have refractive indices that correspond with their relative positionwithin the stack so as to result in a generally smooth refractive indexgradient across the three-dimensional nanostructure. A material having arefractive index gradient, in general, facilitates light penetrationfurther into the material. In some embodiments, a stacked nanostructurehaying a refractive index gradient may be used as a light trappingdevice.

Alternatively, refractive indices of patterned nanostructure layers of athree-dimensional stack may be configured such that the stackednanostructure exhibits an alternating arrangement of refractive indices.For instance, in three-dimensional nanostructure stack, patternednanostructure layers having a relatively low refractive index (e.g.,1.1-1.5) may be positioned so as to alternate with patternednanostructure layers having a relatively high refractive index (e.g.,1.5-4.0, 1.5-2.0, 2.0-3.0). A material having layers that haverefractive indices that alternate between relatively high and relativelylow values will exhibit generally reflective properties. Thus, in someembodiments, a stacked nanostructure having refractive indices that arepositioned in an alternating arrangement between high and low values maybe used as a light reflecting device.

Alternatively, nanoparticle compositions may be patterned with theaddition of a precursor, for example, comprising metal oxide, sol-gel orsol as a dopant or crosslinker. These precursors (e.g., sol-gelprecursor) may be similar to or different from the inorganicnanoparticle being patterned. In some embodiments, the binder materialmay comprise a sol-gel precursor material, such as a suitable metaloxide, metal alkoxide or other material that acts as a precursor forproducing a gel network. Non-limiting examples of sol-gel precursorsinclude cerium sol-gel precursors (e.g., cerium(III) nitratehexahydrate) gadolinia sol-gel precursors (e.g., gadolinium(III) nitratehexahydrate), zirconia sol-gel precursors (e.g., zirconium (IV)(isopropoxide)_(n)(acetyl acetonate)_(m)), and others.

For instance, when it is preferred that charge transfer be permittedbetween interfaces of the nanoparticles, when cured, the binder materialmay exhibit conductive properties. That is, the insulative polymericfeatures of the system may be effectively replaced by a conductivephase. The composition is then exposed to UV radiation so as to cure thebinder material, yielding a conductive phase. FIG. 27 depicts an exampleof a mechanism where a sol-gel precursor material (or any otherappropriate material) mixed with nanoparticles undergoes a step ofhydrolysis and cross-linking.

Any combination of nanoparticles may be incorporated in the nanoparticlecomposition from which the patterned nanostructure is formed.Non-limiting examples of such nanoparticle combinations includeruthenium dioxide (RuO₂) and titanium dioxide (TiO₂), iridium dioxide(IrO₂) and TiO₂, zirconium dioxide (ZrO₂), hafnium dioxide (HfO₂), zincoxide (ZnO), silicon (Si), barium titanate (BaTiO₃), strontium titanate(SrTiO3), aluminum oxide (Al₂O₃) and yttrium oxide (Y₂O₃), cerium oxide(CeO₂) and yttrium oxide stabilized zirconium oxide (YSZ), gadoliniadoped cerium dioxide (GDC), indium oxide (In₂O₃) doped with tin oxide(SnO₂) (indium tin oxide), antimony oxide Sb₂O₃) doped with tin oxide(SnO₂ (antimony tin oxide), Al₂O₃ doped with ZnO (antimony zinc oxide),iron oxide (Fe₂O₃, Fe₃O₄) and iron platinum (FePt), and metalchalcogenides, such as: lead sulfide (PbS), gallium phosphide (GaP),indium phosphide (InP), lead selenide (PbSe), lead telluride (PbTe),amongst others. For example, TiO₂ particles may be initially obtained ina crystalline state. In some embodiments, nanoparticle compositions mayinclude mixtures or dissimilar nanoparticles with dopants includingdyes, fullerenes, infrared emitting nanoparticle (e.g., CeF₃: Yb—Er) orquantum dots. Another embodiment includes patterning nanoparticles ormixtures of dissimilar nanoparticles and/or metal oxide precursors orsols, and/or dopants using NIS. In some embodiments, nanoparticlescomprise carbonaceous-based materials, such as fullerenes, mesoporouscarbon nanoparticles, thermally exfoliated graphite, carbon nanotubes,diamond nanoparticles, graphene, and other forms of carbonaceousmaterials. Other embodiments include the selective exposure of thenanoparticles and mixtures of nanoparticles to thermal, hydrothermal,laser and PulseForge annealing procedures.

Nanoparticle compositions may be applied to substrates in a manner wheresuch compositions may be optionally removable or releasable from therespective substrate once the patterned nanostructure is formed.Accordingly, free-standing patterned nanostructured layers may beformed. As a result, 3D fabrication of patterned nanostructurescomprising suitable nanoparticle mixtures with optionaldopants/additives may occur by subsequent layering of the patternednanostructures in a stacked arrangement and/or at various angles. Anyappropriate number of patterned nanostructure layers may be arranged(e.g., stacked, placed side by side, overlapping, etc.) according to anysuitable configuration to yield a 3D patterned nanostructure. Forexample, such 3D patterned nanostructures may be arranged in a way thatmanipulates electromagnetic radiation in a desirable manner (e.g., lighttrapping, light reflecting, etc.).

Patterned nanostructure layers may be free-standing films or filmssupported by permanent or sacrificial substrates. 3D layered structuresmay include layers of the patterned nanostructures comprisingnanoparticle compositions cured on substrates as well as stacked layersof patterned nanostructures that have been released from theirsubstrates post-cured and appropriately transferred to create the 3Dlayered assembly or combination of layers with or without substrates.Substrates may be released prior to the transfer of the patternednanostructure layers, during the transfer of the patterned nanostructurelayers, or after the transfer of the patterned nanostructure layers.

Methods of release of a patterned nanostructure layer from a substrateinclude but are not limited to use of an intermediate release layerbound to the substrate or a substrate with poor adhesion to thepatterned composition, use of a sacrificial release layer that isremoved during processing using solvents, use of a multi-layer releasestrategy based on orthogonal solvents, or removal of the release layerby use of thermal treatment or electromagnetic irradiation. For example,during fabrication, the nanoparticle composition may be applied directlyto the surface of a substrate which, in some cases, may give rise tostrong adhesion between the nanoparticle composition and the substrateonce the patterned nanostructure is formed. However, in someembodiments, an intermediate layer is provided in between the substrateand the nanoparticle composition such that upon formation of thepatterned nanostructure, the nanoparticle composition may be more easilyreleased from the substrate than would otherwise be the case without theintermediate layer.

In some embodiments, patterned nanostructure layers are prepared usingroll-to-roll manufacturing. For example, a substrate may be coated witha nanoparticle composition using slot die coating or any other suitablemethod and subsequently patterned using roll-to-roll UV-assistednanoimprint lithography or roll-to-roll nanoinscribing. The nanoparticlecomposition can be applied as a coating to any suitable substrate suchas glass, silicon and flexible substrates, such as polymers, metalfoils, poly(ethylene terephthalate) (PET), poly(ethylene naphthalate)(PEN), amorphous glass, and polyimide. The ability to coat and patternsuch nanoparticle compositions on flexible substrates (e.g., plastic)allows for the use of high throughput and continuous manufacturingcapabilities such as roll-to-roll manufacturing. For example, thepatterned mold may be provided as a roll in the shape of a wheel orother arcuate shape and the flexible substrate having a nanoparticlecomposition coated thereon may be placed in contact with and may movealong the patterned mold in a continuous fashion. As the nanoparticlecomposition and substrate system moves continuously along the rotatingpatterned mold while in contact with the patterned mold, an appropriateamount of irradiation (e.g., electromagnetic radiation, heat, UVradiation) may be applied to the composition. Once the nanoparticlecomposition moves out of contact with the patterned mold, the patternednanostructure is suitably cured and formed.

In some embodiments, patterned nanostructure layers may involve coatingnanoparticle compositions on rigid substrates such as silicon wafers orglass or transparent conductive oxides. For example, patternednanostructure layers may be prepared by a roll-to-plate manufacturingprocess where the substrate on which the nanoparticle composition iscoated upon is provided as a plate, yet the patterned mold is providedas a roll, similar to the roll described above for roll-to-rollmanufacturing. Accordingly, as the substrate moves continuously alongthe rotating patterned mold, the nanoparticle composition isappropriately cured. Once the nanoparticle composition comes out ofcontact with the patterned mold, the patterned nanostructure is formed.

The nanoparticles and/or the binder material of the patternednanostructure may be treated in any suitable manner before or afterfinal formation. For example, the nanoparticles may be treated to induceor increase their level of crystallinity. Such treatments can includethermal, hydrothermal processes, treatment with plasmas and UVirradiation. In some embodiments, the patterned nanostructure may betreated to remove organics. Such treatments can include thermal,hydrothermal processes, treatment with plasmas and UV irradiation.

In some embodiments, the patterned nanostructure may be further coatedso as to reduce porosity within the structures or distribute materialswithin the pores or at the surface of the structures. Such processes mayinclude but are not limited to atomic layer deposition, chemical vapordeposition, supercritical fluid deposition, electrodeposition,electroless depositions, surface modification, vapor phase infusion,liquid infusion, supercritical infusion, polymerization, surface inducedpolymerization, radical polymerization, electrochemical polymerization,sol gel chemistry, deposition of self-assembled monolayers,layer-by-layer depositions, chemical grafting at the surface, microwaveinduced grafting or polymerization, UV-induced reaction orpolymerization, or other suitable processes.

Potential Applications

A number of non-limiting applications that certain embodiments relatedto the present disclosure are described below. Such applications anduses are merely exemplary and do not encompass the full scope of theinvention.

Fabrication of Hybrid Photovoltaic Devices with Hierarchical Structure

Hybrid photovoltaic devices constructed from metal-oxide/polymermaterials may require structuring of the active layer to increaseefficiency. By structuring the active layer of hybrid photovoltaicdevices, an increased amount of surface area may be realized, resultingin greater interfacing between the semiconducting materials as well asdirect carrier pathways to the electrodes. Titanium dioxide (TiO₂),amongst other materials such as zinc oxide (ZnO), may be used as a metaloxide material for hybrid photovoltaic devices. Approaches describedherein of patterning the active area of hybrid photovoltaic devices mayrely on the patterning of inorganic nanoparticles, which aresemiconducting and not covalently functionalized, with imprintlithography.

Through approaches in accordance with various embodiments, inorganicnanoparticles are capable of being crystalline, which may be required toobtain efficient hybrid photovoltaic devices, and does not require anadditional high-temperature sintering process to obtain a suitable levelof crystallinity of the inorganic material. The lack of ahigh-temperature sintering process requirement allows for embodimentsdescribed herein to be scaled to continuous manufacturing platforms,such as roll-to-roll (R2R) or roll-to-plate processing, as discussedabove. Non-covalently functionalized inorganic nanoparticles are readilyavailable as highly-loaded (≥20 wt. %) dispersions in water and are ableto undergo a simple solvent exchange to solvents having a higher boilingpoint and lower polarity than water. To further enhance the efficiencyof hybrid photovoltaic devices, dopants and/or dyes, either in the formof nanoparticles or small molecules, can be incorporated into thenanoparticle dispersion with ease.

Electrodes and Electrolytes for Solid Oxide Fuel Cells (SOFCs)

It is beneficial to reduce the overall structural dimension of solidoxide fuel cells (SOFCs) through microfabrication techniques. The termmicro solid oxide fuel cell (μ-SOFCs) is often used when SOFCs areproduced with microfabrication techniques. Such a reduction in magnitudehas potential to achieve reduced ohmic and transport losses, increasethe volumetric energy and power densities, improve the energy conversionefficiency, reduce the operation temperature and unlock newapplications. There is also growing interest in developing well-defined,geometry controlled, nanostructured electrodes, such as cerium dioxideor ceria (CeO₂), and electrolyte materials, such as yttria-stablizedzirconia (YSZ), to improve performance and provide electrodes formodeling of parameters such as oxygen reduction, diffusion length andnano-ionic effects. Patterning the interface created between theelectrode and the electrolyte material in μ-SOFCs with nanoscopicfeatures achievable with NIL may be performed.

Zirconium dioxide, or zirconia (ZrO₂), nanoparticles with various yttria(Y₂O₃) dopant levels, or YSZ nanoparticles, may be incorporated intonanoparticle compositions to create patterned nanostructures. Y₂O₃dopant levels may range from 3 mol. % to 10 mol. %. The nanoparticlescrystallite size ranges from 10-12 nm and are available as acidicaqueous dispersions. The substrate for SOFC will be a YSZ crystal andwill be patterned with either CeO₂ or YSZ nanoparticles. Patterning ofthese materials may increase the area of the triple phase boundary line,which is where fuel may come into contact with the electrode and theelectrolyte, which in this case is either patterned CeO₂ or YSZnanoparticles.

Structuring of Transparent Conductive Oxide (TCO) Materials

Transparent conductive oxide (TCO) materials, such as indium doped tinoxide (ITO) and zinc oxide (ZnO), have been a reliable source oftransparent electrodes due to high optical transparency and highelectrical conductivities. Applications that utilize TCOs includedisplays, solar cells and organic light emitting diodes (OLEDs). Tofurther increase the efficiencies of the applications mentioned above,the TCOs may require patterning into arbitrary structures to eitherincrease surface area or to trap light. Approaches described herein forpatterning nanoparticles will not only allow TCO materials to bepatterned into desired geometries but will also allow the patterningapproach to be applied to roll-to-roll manufacturing platforms for moreaffordable production of transparent electrodes.

Nanopatterned High Performance Lithium Ion Battery Anodes

For rechargeable lithium (Li) ion batteries to be effective forautomobile and stationary storage applications, power density, cost andcycling lifetime should be improved. Increasing the storage capacity ofanode materials through the incorporation of silicon has been studied.Silicon possesses the highest theoretical gravimetric and volumetricstorage capacities (Li₁₅Si₄≈3579 mA h/g, 8340 mA h/mL) and has beenunder study. The drawback of silicon as an anode material is the largevolumetric expansion during cycling, which causes the anode to fractureand thus reduces electrical contact and subsequent performance.Nanoparticles of silicon may be better suited to accommodate the volumechange than the bulk counterpart. However, due to the high surfaceenergy of silicon, the nanomaterial will begin to aggregate throughelectrical sintering and result in reduced anode performance.

One way to reduce this electrical sintering is to use a mesoporouscarbon nanoparticle in combination with phenol capped siliconnanoparticles. To additionally increase the surface area and, in turn,the lithium storage capacity, these mixed nanoparticle systems can bepatterned with high aspect ratio features to be used as high performancelithium ion battery anodes. The nanostructured features will increasethe surface area, which will yield higher intercalation of the lithiumions and overall higher storage capacities. This mixed particle systemshould reduce the drawbacks of silicon by itself, without sacrificingthe lithium storage capacity and create lithium ion anodes with extendedlifetimes.

Anti-Reflective Patterning and Coating

Anti-reflective coatings may be constructed through a multilayer coatingthat has a graded transition in refractive index that reduces therefractive index from air (n=1.0) to the substrate of interest(n_(PET)=1.57, n_(Glass)=1.52). However, through this approach amultilayer coating may be needed, whereas by patterning a nanoparticlecomposite with tunable refractive index, this process can be achievedwith only one coating, which has a patterned nanostructure (e.g.,nanoimprinted). Features of the patterned nanostructure may allow for agraded refractive index from the air to the substrate. Features that areused with anti-reflective coatings may be inspired by a moth's eye.Moth's use a non-close packed nipple nanostructure to reduce thereflectance of their eyes. These non-close packed nipples allow for agraded refractive index from 1.0 to the refractive index of thesubstrate, reducing the reflectance and in turn, increasing thetransmittance. By forming a patterned nanostructure (e.g., viananoimprinting) from the UV-sensitive nanoparticle composition, thereflectance of the coating can be significantly reduced when compared tothe uncoated substrate.

The nanoparticles that will be utilized for these compositions are basedon high refractive index metals and metal oxides that do not absorb orfluoresce in the visible spectrum. Some nanoparticles of interest areTiO₂, CeO₂, ZrO₂, indium tin oxide (ITO), and metal chalcogenides, suchas: lead sulfide (PbS), gallium phosphide (GaP), indium phosphide (InP),lead selenide (PbSe), lead telluride (PbTe), etc. These nanoparticlesmay have particle sizes less than 40 nm, as well as the mean particleaggregate size will be less than this in order to be below the Rayleighscattering limit. These nanoparticles may be combined with a 365 nmUV-sensitive photoresist in either a polar aprotic solvent or aqueousbased composition. The TiO₂ nanoparticles have a tunable refractiveindex of 1.58 (neat photoresist) to 1.9 (for 90 wt % TiO₂ nanoparticles)at 800 nm. Once an appropriate mold or photoresist is made, the coatingcan be patterned (e.g., nanoimprinted) with a non-close packed array ofdifferent spacing to create anti-reflective coatings.

Creation of Metastructures and Metamaterials

Metamaterials are comprised of metals or dielectrics that are patternedat length scales below the operating wavelength of interest. Thesepatterned materials are arranged in different geometries to yieldresponses to electromagnetic excitation that does not exist in nature.The alteration of the electromagnetic waves incident upon theseengineered metamaterials can result in negative refraction,subwavelength imaging, and cloaking. However, these metamaterials areoften limited to narrow bands of frequencies and the fabrication atlarge scales is difficult and tedious. Embodiments described herein canremedy the scalability problem by using a large scale manufacturingplatform, roll-to-roll manufacturing. A solution processablemetamaterial can be created by subsequent layering of patterned metaland/or dielectric nanoparticle free standing structures.

Creation of Photonic Bandgap Materials

Photonic bandgap materials may be created using vacuum processingtechniques, interference lithography, or direct write techniques, all ofwhich are limited to small scalability or low throughput or both.Aspects described herein enables a solution processable photonic bandgapstructure by subsequent layering of patterned high refractive index freestanding structures.

EXAMPLES

The following examples are intended to illustrate certain embodiments ofthe present invention, but are not to be construed as limiting and donot exemplify the full scope of the invention.

Materials

Metal oxide nanoparticles were obtained stabilized by either acid orbase. Several different nanoparticle systems were employed, includingTiO₂, Fe₂O₃, CeO₂ and ZrO₂. Norland optical adhesive 60 (NOA60) wasobtained from Norland Products Inc. FIG. 26 shows the proposed chemicalstructure of NOA60. Poly(acrylic acid) (PAA, 1800 g/mol), polyvinylalcohol) (PVOH, Mowiol 4-88, Mowiol 40-88) and acetyl acetone (AcAc)ReagentPlus® 99% were obtained from Sigma-Aldrich. Bimodal polystyrene(PS, 45,000 g/mol) was obtained from Scientific polymers. Methanol(MeOH) and N-methyl pyrrolidone (NMP) were obtained from FisherScientific. Titanium diisopropoxide bis(acetylacetonate), 70%, solutionin isopropanol and(heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane wereobtained from Gelest. Sylgard 184 was obtained from Ellsworth Adhesives.Anatase and rutile titanium dioxide nanoparticles were obtained asaqueous dispersions from a number of vendors, including Nanostructuredand Amorphous Materials, Inc., U.S, Research Nanomaterials. Inc. andEvonik Industries, Inc. Cerium dioxide dispersions were obtained as anacidic aqueous dispersion from Nyacol Nano Technologies, Inc. Zirconiumdioxide nanoparticles were obtained as an acidic aqueous dispersion fromNyacol Nano Technologies, Inc. and MEL Chemical, Inc. Yttria-stabilizedzirconium (YSZ) dioxide nanoparticles were obtained as acidicdispersions in different yttria compositions from MEL Chemicals, Inc.

Soft Mold Fabrication Preparation

Molds were fabricated from silicon gratings with dimensions ranging from100 nm to 800 nm line widths, 100 nm to 500 nm depths and 500 nm to 1600nm pitch. These silicon master molds were initially made hydrophobic byapplying a self-assembled monolayer to reduce adhesion between the moldand silicon. To react the self-assembled monolayer with the siliconmaster mold, the mold is first treated with oxygen plasma, then a gasphase reaction of(heptadecafluoro-1,1,2,2-tetrahydrodecyl)dimethylchlorosilane occurs at80 C for 24 hours. Once the silicon molds were treated, siliconereplicas were created. The silicone used was Slygard 184 with a 1:10ratio of curing agent to base. Once the silicone was well mixed anddegassed, the silicon master mold was replicated by thermally curing thesilicone at 70 C for 3 hours.

Example 1 Solvent Exchange of Metal Oxide Nanoparticles

A 250 mL beaker was charged with 100 g of the specific acidic or basicmetal oxide nanoparticle dispersion or mixed metal oxide nanoparticledispersion and 50 g each of NMP and MeOH was added. The solvent was thenevaporated until most of the residual water was removed. Once the waterwas removed the solids remaining were diluted to the desiredconcentration with a 50:50 mixture of NMP and MeOH. The system wassubjected to ultra-sonication for 5 minutes to completely re-dispersethe nanoparticles into the organic solvents, while maintaining thesolution at room temperature with a recirculating water bath. Thedispersion after sonication was translucent.

Example 2 High Refractive Index Planar TiO₂ Hard Coat

Solvent exchanged titanium dioxide nanoparticles using the procedurefrom Example 1 (13.2 wt % TiO₂ in a 50:50 mixture of NMP: MeOH) wasadded to a 20 mL glass vial along with a 13.2 wt % solution of NOA60 inNMP in amounts varying from 0 wt % NOA60 to 90 wt % NOA60. The amount ofNOA60 that was added was adjusted to obtain the desired refractiveindex. FIG. 20 illustrates the refractive index versus wavelength ofplanar patterned nanoparticle nanostructures based on TiO₂ (5 nm to 30nm in particle size) and a commercially available thiol-ene basedphotoresist (NOA60). The solution was filtered through a 0.2 micron PTFEfilter and then spun coat on a substrate (silicon, glass, or plastic,depending on the application) in a low humidity environment at 3000 rpmuntil no solvent remained (approximately 2 minutes). The coating wasthen irradiated with 365 nm UV light for 15 min with an intensity of 12mW/cm² under a nitrogen environment.

The as described planar coatings exhibit greater than 90% transparencyand refractive index values, at a wavelength of 800 nm, ranging from1.58 for the neat photoresist to 1.9 for 10 wt % NOA60. FIG. 21 showsUV-Vis spectra of planar patterned nanoparticle nanostructures comprisedof a TiO₂ nanoparticle (5 nm to 30 nm in particle size) and acommercially available thiol-ene based photoresist (NOA60). FIG. 22shows X-ray diffraction results of the planar patterned nanoparticlenanostructures showing the characteristic peaks for crystalline anataseTiO₂ without a high temperature calcination step with varying amounts ofNOA60. FIG. 23 shows FT-IR spectra of patterned nanoparticlenanostructures composed of anatase TiO₂ (5 nm to 30 nm in particle size)with and NOA60. FIG. 24 shows a comparison of photo-DSC thermograms ofpatterned nanoparticle nanostructures of 100 wt % NOA60, 100 wt % TiO₂,90 wt % TiO₂ and 10 wt % NOA60, and 50 wt % TiO₂ and 50 wt % NOA60.

The adhesion to the silicon substrate is extremely good as can be seenin FIG. 25, which shows adhesion measurements of different patternednanostructures with varying amounts of NOA60 in relation to TiO₂ usingASTM D 3359 with 810 scotch tape. The RMS roughness of the coatings isalso quite small (less than 6 nm). FIG. 27 shows the crosslinkingmechanism of a titanium sol titanium diisopropoxide bis(acetylacetonate)at 365 nm UV light.

RMS roughness values of planar films based on a nanoparticlenanostructures comprising TiO₂ (5 nm to 30 nm particle sizes) using acommercially available thiol-ene based photoresist (NOA60) at differentcompositions are provided in FIG. 28.

Example 3 Patterned TiO₂ Nanoparticle Nanocomposites Using OrganicSolvent Dispersible Formulations

Solvent exchanged titanium dioxide nanoparticles using the procedure inExample 1 (13.2 wt % TiO₂ in a 50:50 mixture of NMP: MeOH) was added toa 20 mL glass vial along with a 13.2 wt % solution of NOA60 in NMP inamounts varying from 0 wt % NOA60 to 90 wt % NOA60. The amount of NOA60was adjusted to obtain the desired refractive index, as can be seen inFIG. 20. The solution was filtered through a 0.2 micron PTFE filter andthen spun coat on a substrate (silicon, glass, or plastic, depending onthe application) in a low humidity environment at 3000 rpm for 30seconds and then the mold was placed on top of the substrate with thecoating. The coating was then irradiated with 365 nm UV light for 15 minwith an intensity of 12 mW/cm² under a nitrogen environment. The moldwas carefully peeled off of the coating and the characteristicdiffraction pattern for the particular mold could be seen over theentire film. The imprinted structures of the different molds andcompositions with different refractive indices are shown in FIGS. 2Athrough 6.

FIGS. 2A-2F illustrates 2D and 3D AFM images of patterned TiO₂nanoparticle nanostructures (5 nm to 30 nm in particle size) using acommercially available thiol-ene based photoresist (NOA60). Thedimensions of the photoresist mold are 500 nm line width and 500 nmdepth with a periodicity of 1.0 micron. FIGS. 2A-2F shows images ofsamples where relative concentrations of nanoparticles and binder in thenanoparticle compositions are follows: A) 100 wt % TiO₂ and 0 wt %NOA60, B) 90 wt % TiO₂ and 10 wt % NOA60, C) 80 wt % TiO₂ and 20 wt %NOA60, D) 70 wt % TiO₂ and 30 wt % NOA60, E) 60 wt % TiO₂ and 40 wt %NOA60, F) 50 wt % TiO₂ and 50 wt % NOA60.

FIG. 3 shows SEM images of patterned TiO₂ nanoparticle nanostructures (5nm to 30 nm in particle size) using a commercially available thiol-enebased photoresist (NOA60) with mold dimensions of 500 nm line width, 500nm depth and 1.0 micron pitch. FIG. 3 shows images of samples whererelative concentrations of nanoparticles and binder in the nanoparticlecompositions are follows: A) 90 wt % TiO₂ and 10 wt % NOA60, B) 80 wt %TiO₂ and 20 wt % NOA60, C) 70 wt % TiO₂ and 30 wt % NOA60, and 50degrees tilted SEM images of D) 90 wt % TiO₂ and 10 wt % NOA60, E) 80 wt% TiO₂ and 20 wt % NOA60, F) 70 wt % TiO₂ and 30 wt % NOA60.

FIG. 4 shows SEM images of a triangular grating of patterned TiO₂nanoparticle nanostructures (5 nm to 30 nm particle size) using acommercially available thiol-ene based photoresist (NOA60) with molddimensions of 150 nm line width, 500 nm depth and 1.0 micron. FIG. 4shows images of samples where the relative concentration of thenanoparticle composition is 90 wt % TiO₂ and 10 wt % NOA60. A) and B)show top down SEM images; and C) and D) show SEM images 50 degreestilted.

FIG. 5 shows rectangular via structures of patterned TiO₂ nanoparticlenanostructures (5 nm to 30 nm in particle size) using a commerciallyavailable thiol-ene based photoresist (NOA60) with mold dimensions of1.5 micron width, 1.5 micron height, 500 nm depth, and 2 micron pitch.FIG. 5 depicts images of samples where the relative concentration of thenanoparticle composition is 90 wt % TiO₂ and 10 wt % NOA60. A), B), andC) are top down SEM images at different magnifications and D), E) and F)are 50 degree tilted SEM images at different magnifications.

FIG. 6 shows circular via structures of patterned TiO₂ nanoparticlenanostructures (5 nm to 30 nm in particle size) using a commerciallyavailable thiol-ene based photoresist (NOA60) with mold dimensions of1.5 micron width, 1.5 micron height, 500 nm depth, and 2 micron pitch.FIG. 6 depicts images of samples where the relative concentration of thenanoparticle composition is 90 wt % TiO₂ and 10 wt % NOA60. A) is a topdown SEM images, and B) and C) are 50 degree tilted SEM images atdifferent magnifications.

Example 4 Patterned TiO₂Nanoparticle Nanocomposites Using WaterDispersible Formulations

The obtained acidic titanium dioxide nanoparticles were added to a 20mL, glass vial along with a water dispersible, UV-curable photoresist.The solution was filtered through a 0.2 micron PTFE filter and then spuncoat on a substrate (can be silicon, glass, or plastic. depending on theapplication) in a low humidity environment at 3000 rpm for 30 secondsand then the mold was placed on top of the substrate with the coating.The coating was then irradiated with 365 nm UV light for 15 min with anintensity of 12 mW/cm² under a nitrogen environment. The mold wascarefully peeled off of the coating and the characteristic diffractionpattern for the particular mold could be seen over the entire film.

Example 5 Patterned Nanoparticle Composites with Organic Solvent BasedTitania Sols

Solvent exchanged titanium dioxide nanoparticles using the procedure inExample 1 (13.2 wt % TiO₂ in a 50:50 mixture of NMP: MeOH) was added toa 20 mL glass vial along with a 70 wt % solution of titaniumdiisopropoxide bis(acetylacetonate) in isopropanol amounts varying from0 wt % titanium diisopropoxide bis(acetylacetonate) to 90 wt % titaniumdiisopropoxide bis(acetylacetmate). The amount of titaniumdiisopropoxide bis(acetylacetonate) that was added was adjusted toobtain the desired refractive index. The solution was filtered through a0.2 micron PTFE filter and then spun coat on a substrate (silicon,glass, or plastic, depending on the application) in a low humidityenvironment at 3000 rpm for 30 seconds and then the mold was placed ontop of the substrate with the coating. The coating was then irradiatedwith 365 nm UV light for 15 min with an intensity of 12 mW/cm². Theapparent crosslinking mechanism of the titania sol can be seen in FIG.27. The mold was released from the coating and the characteristicdiffraction pattern for the particular mold could be seen over theentire film.

FIG. 29 shows high aspect ratio, cross sectional SEM images at differentmagnifications for a nanoparticle composition that was uncalcined, 90 wt% TiO₂ and 10 wt % titanium diisopropoxide bis(acetylacetonate), using amaster mold having dimensions of 250 nm line width, 500 nm depth, and500 nm pitch. FIG. 30 shows high aspect ratio, cross sectional SEMimages at different magnifications for a nanoparticle composition thatwas calcined at 650 C, 90 wt % TiO₂ and 10 wt % titanium diisopropoxidebis(acetylacetonate),using a master mold having dimensions of 250 amline width, 500 am depth, and 500 nm pitch. These images show that it ispossible, using techniques and processes described herein, to fabricatefeatures extending above the surface that are small (e.g., 50-200 nmwide, 150-300 nm tall) and have a high aspect ratio (e.g., 1.5:1, 2:1,2.5:1, 3:1, 3.5:1, 4:1, 5:1, etc.), in a repeatable manner.

Example 6 Patterned Nanoparticle Composites using Water DispersibleTitania Sols

The obtained acidic titanium dioxide nanoparticles were added to a 20mL, glass vial along with a 70 wt % solution of titanium diisopropoxidebis(acetylacetonate) in isopropanol in amounts varying from 0 wt %titanium diisopropoxide bis(acetylacetonate) to 90 wt % titaniumdiisopropoxide bis(acetylacetonate). The amount of titaniumdiisopropoxide bis(acetylacetonate) that was added was varied to obtainthe desired refractive index. The silicone replica mold was exposed to 5minutes of oxygen plasma to improve the wetting of the water/IPAsolution. The solution was filtered through a 0.2 micron nylon filterand then spun coat on a substrate (silicon, glass, or plastic, dependingon the application) in a low humidity environment at 3000 rpm for 30seconds and then the mold was placed on top of the substrate with thecoating. The coating was then irradiated with 365 nm UV light for 15 minwith an intensity of 12 mW/cm² under a nitrogen environment.

The apparent crosslinking mechanism of the titania sol is shown in FIG.27. The mold was carefully peeled off of the coating and thecharacteristic diffraction pattern for the particular mold could be seenover the entire film. FIG. 7 shows SEM of the imprinted patterned TiO₂nanoparticle nanostructures (5 nm to 30 nm in particle size) and atitanium sol (titanium diisopropoxide bis(acetylacetonate)) with molddimensions of 500 nm line width, 500 nm depth and 1.0 micron pitch. FIG.7 shows SEM images of samples where relative concentrations ofnanoparticles and binder in the nanoparticle compositions are follows:A) 50 wt % TiO₂ and 50 wt % titanium diisopropoxidebis(acetylacetonate), C) 90 wt % TiO₂ and 10 wt % titaniumdiisopropoxide bis(acetylacetonate) shown as top down SEM images; and B)50 wt % TiO₂ and 50 wt % titanium diisopropoxide bis(acetylacetonate),D) 90 wt % TiO₂ and 10 wt % titanium diisopropoxide bis(acetylacetonate)shown as 50 degrees tilted SEM images.

Example 7 Patterned CeO₂ Nanoparticle Composites using Organic SolventDispersible Formulations

Solvent exchanged cerium dioxide nanoparticles using the procedure inExample 1 (10 wt % CeO₂ in a 50:50 mixture of NMP: MeOH) was added to a20 mL glass vial along with a 10 wt % solution of NOA60in NMP in amountsvarying from 0 wt % NOA60to 90 wt % NOA60. The solution was filteredthrough a 0.2 micron PTFE filter and then spun coat on a substrate(silicon, glass, or plastic, depending on the application) in a lowhumidity environment at 3000 rpm for 30 seconds and then the mold wasplaced on top of the substrate with the coating. The coating was thenirradiated with 365 nm UV light for 15 min with an intensity of 12mW/cm² under a nitrogen environment. The mold was carefully peeled offof the coating and the characteristic diffraction pattern for theparticular mold could be seen over the entire film. FIG. 8 shows topdown SEM images of the imprinted nanostructures comprising 100 wt % CeO₂nanoparticles (10 nm to 20 nm particle size) with mold dimensions of 500nm line width, 500 nm depth and 1.0 micron pitch.

Example 8 Patterned CeO₂ Nanoparticle Composites with Cerium Sol-GelPrecursors

Solvent exchanged cerium dioxide nanoparticles using the generalprocedure described in Example 1 (with 10 wt % CeO₂ in a 50:50 mixtureof NMP: MeOH) was added to a 20 mL glass vial along with a 10 wt %solution of cerium(III) nitrate hexahydrate (Ce(III)(NO₃)₃) sol-gelprecursor in NMP in amounts varying from 0 wt % Ce(III)(NO₃)₃ to 90 wt %Ce(III)(NO₃)₃. The solution was filtered through a 0.2 micron PTFEfilter and then spun coat on a substrate (silicon, glass, or plastic,depending on the application) in a low humidity environment at 3000 rpmfor 30 seconds and then the mold was placed on top of the substrate withthe coating.

After a sufficient time passed for the coating to dry, the mold was thencarefully peeled off of the coating and the characteristic diffractionpattern for the particular mold could be seen over the entire film. FIG.9 shows uncalcined SEM images of samples where relative concentrationsof nanoparticles and binder in the nanoparticle compositions are 80 wt %CeO₂ and 20 wt % Ce(III)(NO₃)₃: top row [A), B) and C)] are shown as topdown SEM images and bottom row [E), F), G)] are shown as SEM imagestilted 50 degrees using a master mold having dimensions of 500 nm linewidth, 500 nm depth, and 1000 nm pitch. These compositions can then becalcined at elevated temperatures without significant shrinkage to thefilm thickness, as indicated in FIG. 10. FIG. 10 depicts the percentloss in thickness of planar films composed of CeO₂nanoparticles andCe(III)(NO₃)₃, calcined at 450 C and 650 C, as functions of nanoparticleloading (weight and volume percentages), shown to be less than 35% wherethe percent weight of CeO₂ nanoparticles is greater than 35 wt %.

FIG. 11 shows a single composition, 100 wt % CeO₂ and 0 wt %Ce(III)(NO₃)₃ after calcination at 1000 C: top row [A), B) and C)] areshown as top down SEM images and the bottom row [E), F), G)] are shownas SEM images tilted 60 degrees using a master mold having dimensions of500 run line width, 500 nm depth, and 1000 nm pitch. FIG. 12 depicts SEMimages of a patterned nanostructure including 90 wt % CeO₂ and 10 wt %Ce(III)(NO₃)₃ after calcination at 1000 C: top row [A), B) and C)] areshown as top down SEM images and the bottom row [E), F), G)] are shownas SEM images tilted 60 degrees using a master mold having dimensions of500 nm line width, 500 nm depth, and 1000 nm pitch. Upon calcination at1000 C there is significant coarsening of the structure, and thuscrystallization, as evidenced by the reduction in the full width at halfmaxima of the <111> reflection as seen in FIG. 13, which shows the XRDspectra for CeO₂ nanoparticles mixed with Ce(III)(NO₃)₃ a) beforecalcination and b) after calcination.

FIG. 31 shows high aspect ratio, cross sectional SEM images at differentmagnifications for a nanoparticle composition that was uncalcined, 90 wt% CeO₂ and 10 wt % Ce(III)(NO₃)₃, using a master mold having dimensionsof 250 nm line width, 500 nm depth, and 500 nm pitch. FIG. 32 shows highaspect ratio, cross sectional SEM images at different magnifications fora nanoparticle composition that was calcined at 650 C, 90 wt % CeO₂ and10 wt % Ce(III)(NO₃)₃, using a master mold having dimensions of 250 nmline width, 500 nm depth, and 500 nm pitch. As such, techniques andprocesses described herein provide for repeatable fabrication of small,high-aspect ratio features.

Example 9 Patterning of Gadolinia doped CeO₂ Nanoparticle Compositeswith Organic Solvent Dispersible Formulations

Solvent exchanged cerium dioxide nanoparticles using the generalprocedure described in Example 1 (with 10 wt % CeO₂ in a 50:50 mixtureof NMP: MeOH) was added to a 20 mL glass vial along with a 10 wt %solution of gadolinium(III) nitrate hexahydrate (Ce(III)(NO₃)₃) in NMPin amounts varying from 0 wt % Gd(III)(NO₃)₃ to 90 wt % Gd(III)(NO₃)₃.The solution was filtered through a 0.2 micron PTFE filter and then spuncoat on a substrate (silicon, glass, or plastic, depending on theapplication) in a low humidity environment at 3000 rpm for 30 secondsand then the mold was placed on top of the substrate with the coating.

A sufficient time was allowed to pass for the coating to thy and themold was carefully peeled off of the coating. The characteristicdiffraction pattern for the particular mold could be seen over theentire film. X-ray photoelectron spectroscopy (XPS) has shown thatgadolinia is present after calcination at 1000 C of the patternedgadolinia doped CeO₂ nanoparticle formulations. FIG. 14 shows the XRDspectra of the patterned CeO₂ nanoparticle formulations with gadolinia(Gd(III)(NO₃)₃) incorporated as the binder after calcination at 1000 C,showing a shift to a reduced 2θ upon incorporation of gadolinia withinthe CeO₂ lattice, indicating the presence of gadolinia.

Example 10 Patterning of ZrO₂ Nanoparticle Composites with OrganicSolvent Dispersible Formulations

Zirconium dioxide nanoparticles were used in the basic proceduresdescribed above. Solvent exchanging zirconium dioxide nanoparticlesusing the procedure in Example 1 was done by adding it to a 20 mL glassvial along with a solution of NOA60 in NMP in amounts varying from 0 wt% NOA60to 90 wt % NOA60. The solution was sent through a 0.2 micron PTFEfilter and then spun coat on a substrate (silicon, glass, or plastic,depending on the application) in a low humidity environment at 3000 rpmfor 30 seconds and then the mold is put on top of the substrate with thecoating. The coating was then irradiated with 365 nm UV light for 15 minwith an intensity of 12 mW/cm² under a nitrogen environment. The moldwas then carefully peeled from the coating.

Example 11 Synthesis of Zirconium (IV) (Isopropoxide)_(n)(AcetylAcetonate)_(m)

A 100 mL, amber glass vial was placed into a glass drying oven at 120°C. to remove the absorbed water. This vial was then charged with 20 mLof zirconium(IV) n-propoxide and between 4 mL and 10 mL of acetylacetone, with stirring. An exothermic reaction takes place to yield azirconium (IV) (isopropoxide)_(n)(acetyl acetonate)_(m) sol-gelprecursor. A sol-gel precursor that gave favorable results was zirconium(IV) (isopropoxide)_(2.6)(acetyl acetonate)_(1.4), which was solublewithin NMP.

Example 12 Patterned ZrO₂ Nanoparticle Composites with Zirconium Sol-GelPrecursors

Solvent exchanged zirconium dioxide nanoparticles using the generalprocedure described in Example 1 (with 13.2 wt % ZrO₂ in a 50:50 mixtureof NMP: MeOH) was added to a 20 mL glass vial along with a 30 wt %solution of zirconium(IV) (isopropoxide)_(n)(acetylacetonate)_(m) (ZPA)in n-propanol in amounts varying from 0 wt % ZPA to 90 wt % ZPA. Theamount of ZPA that was added was adjusted to obtain the desiredrefractive index or dielectric constant.

The solution was filtered through a 0.2 micron PTFE filter and then spuncoat on a substrate (silicon, glass, or plastic, depending on theapplication) in a low humidity environment at 3000 rpm for 30 secondsand then the mold was placed on top of the substrate with the coating.The coating was then irradiated with 365 nm UV light for 15 min with anintensity of 12 mW/cm². The mold was released from the coating and thecharacteristic diffraction pattern for the particular mold could be seenover the entire film.

FIGS. 15A-15F shows AFM images of samples patterned using solventassisted UV-NIL (UV dose of approximately 10.7 J/cm²) beforecalcination, where relative concentrations of nanoparticles and binderin the nanoparticle compositions are follows: A) 50 wt % ZrO₂ and 50 wt% ZPA, B) 60 wt % ZrO₂ and 40 wt % ZPA, C) 70 wt % ZrO₂ and 30 wt % ZPA,D) 80 wt % ZrO₂ and 20 wt % ZPA, E) 90 wt % ZrO₂ and 10 wt % ZPA and F)100 wt % ZrO₂ and 0 wt % ZPA. FIGS. 16A-16F shows AFM images of thesamples of FIGS. 15A-15F after calcination at 1000 C where relativeconcentrations of nanoparticles and binder in the nanoparticlecompositions are follows: A) 50 wt % ZrO₂ and 50 wt % ZPA, B) 60 wt %ZrO₂ and 40 wt % ZPA, C) 70 wt % ZrO₂ and 30 wt % ZPA, D) 80 wt % ZrO₂and 20 wt % ZPA, E) 90 wt % ZrO₂ and 10 wt % ZPA and F) 100 wt % ZrO₂and 0 wt % ZPA.

Example 13 3-D Fabrication of Patterned Nanoparticle Composites

In order to create a water releasable free standing structure, atri-layer strategy using orthogonal solvents was employed. The firstlayer was the water soluble layer, which can be composed of poly(acrylicacid) (PAA), poly(vinyl alcohol) (PVOH), poly(styrene sulfonic acid),etc., and allows the structure to be free standing at the air-waterinterface until it is picked up.

A 5 wt % PVOH (Mowiol 4-88) solution in water was spun coat at 3000 rpmat ambient conditions and baked at 150 C for 1 minute to remove anyresidual solvent. The second layer was a bimodal poly(styrene) (PS,45,000 g/mol), which acts as a barrier to the next nanoparticlecomposite layer. A 5 wt % PS solution in toluene was spun coat on top ofthe PVOH layer and baked at 90 C for 1 minute. Finally the solventexchanged titanium dioxide nanoparticles using the general proceduredescribe in Example 1 (with 13.2 wt % TiO₂ in a 50:50 mixture of NMP:MeOH) was added to a 20 ml, glass vial along with a 13.2 wt % solutionof NOA60in NMP in amounts varying from 0 wt % NOA60 to 90 wt % NOA60 canbe spun coat. The amount of NOA60 that was added can be varied to obtainthe desired refractive index, as can be seen in FIG. 20.

The solution was filtered through a 0.2 micron PTFE filter and then spuncoat on a substrate (silicon, glass, or plastic, depending on theapplication) in a low humidity environment at 3000 mm for 30 seconds andthen the mold was placed on top of the substrate with the coating. Thecoating was then irradiated with 365 nm UV light for 15 min with anintensity of 12 mW/cm² under a nitrogen environment. The mold wascarefully peeled off of the coating and the characteristic diffractionpatterns for the particular mold could be seen over the entire film.

Once the tri-layer has been created a water bath is then used to releasethe PS and patterned nanoparticle composite structure from thesubstrate. Then another substrate that was previously patterned was thenpicked up with the film at the air water interface (which may occur atany angle desired by the user). FIG. 17 shows SEM images of a crossdouble layer 3D patterned TiO₂ nanoparticle nanostructure (5 nm to 30 nmparticle sizes) using a commercially available thiol-ene basedphotoresist (NOA60) with mold dimensions of 500 nm line width, 500 nmdepth and 1.0 micron pitch. The relative compositions of nanoparticleand binder were 50 wt % TiO₂ and 50 wt % NOA60. FIG. 17 shows top downSEM images in A), B), and C) and SEM images tilted 50 degrees for D),E), and F) at different magnifications. FIG. 18 depicts SEM images of afour layer 3D photonic crystal patterned TiO₂ nanoparticle nanostructurewhere the relative composition of nanoparticle and binder were 50 wt %TiO₂ and 50 wt % NOA60. FIG. 18 shows top down SEM images at differentmagnifications. FIG. 19 illustrates a reflectance spectra of a 6 layerlog-pile photonic crystal. The spectra shows the capability of these 3Dphotonic crystals to reflect a large amount of the electromagneticspectrum, depending on the lattice parameters of the patternednanoparticle composite.

Example 14 Patterned Nanoparticle Composites Using Photolithography

Solvent exchanged titanium dioxide nanoparticles using the generalprocedure described in Example 1 (with 13.2 wt % TiO₂ in a 50:50 mixtureof NMP: MeOH) was added to a 20 mL glass vial along with a 13.2 wt %solution of NOA60in NMP in amounts varying from 0 wt % NOA60to 90 wt %NOA60. The amount of NOA60was adjusted to obtain the desired refractiveindex, as can be seen in FIG. 21. The solution was filtered through a0.2 micron PTFE filter and then spun coat on a substrate (silicon,glass, or plastic, depending on the application) in a low humidityenvironment at 3000 rpm for 30 seconds and then the mold was placed ontop of the substrate with the coating. A lithographic mask is placed ontop of the films and the film is irradiated with UV light to induce acrosslinking reaction in the exposed regions of the film. The mask isremoved and the unexposed regions are removed using solvent to produce apatterned nanoparticle composition.

Example 15 Patterned Nanoparticle Compositions Using UV-AssistedNanoinscribing

Solvent exchanged titanium dioxide nanoparticles using the generalprocedure described in Example 1 (with 13.2 wt % TiO₂ in a 50:50 mixtureof NMP: MeOH) may be added to a 20 mL glass vial along with a 13.2 wt %solution of NOA60in NMP in amounts varying from 0 wt % NOA60 to 90 wt %NOA60. The amount of NOA60 may be adjusted to obtain the desiredrefractive index, as can be seen in FIG. 20. FIG. 20 shows a graph ofrefractive index as a function of wavelength for the nanoparticlenanocomposites. The solution may be filtered through a 0.2 micron PTFEfilter and then spun coat on a substrate (silicon, glass, or plastic,depending on the application) in a low humidity environment at 3000 rpmfor 30 seconds. A transparent quartz master containing 200 nm groves maybe brought into contact with the nanoparticle formulation and thesubstrate. Then the substrate may be translated relative to the mastersuch that nanoparticle formulation is directed through the channels inthe quartz master while the master and the film may be illuminated by UVlight, which would cross-link the nanoparticle formulation to produce apattern. The patterned substrate may be subject to additionalillumination after contact with the master to induce additionalcrosslinking to produce a patterned nanoparticle composition.

Example 16 Patterned Nanoparticle Compositions with Titania Sols UsingUV-Assisted Nanoinscribing

Solvent exchanged titanium dioxide nanoparticles prepared using thegeneral procedure described in Example 1 (with 13.2 wt % TiO₂ in a 50:50mixture of NNW: MeOH) may be added to a 20 mL glass vial along with a 70wt % solution of titanium diisopropoxide bis(acetylacetonate) inisopropanol in amounts varying from 0 wt % titanium diisopropoxidebis(acetylacetonate) to 90 wt % titanium diisopropoxideb(acetylacetonate). The amount of titanium diisopropoxidebis(acetylacetonate) that is added may be adjusted to obtain the desiredrefractive index. The solution may be filtered through a 0.2 micron PTFEfilter and then spun coat on a substrate (silicon, glass, or plastic,depending on the application) in a low humidity environment at 3000 rpmfor 30 seconds. A transparent quartz master containing 200 nm groves maybe brought into contact with the nanoparticle formulation and thesubstrate. Then the substrate may be translated relative to the mastersuch that nanoparticle formulation is directed through the channels inthe quartz master while the master and the film may be illuminated by UVlight, which may cross-link the nanoparticle formulation to produce apattern. The patterned substrate may be subject to additionalillumination after contact with the master to induce additionalcrosslinking to produce a patterned nanoparticle composition.

Example 17 Patterned Nanoparticle Compositions using Optical Flash LampPulse Curing (Photonic Curing) System

Organic solvent based nanoparticle dispersions of indium doped tin oxide(ITO) or antimony doped tin oxide (ATO) nanoparticles prepared using thegeneral procedure described in Example 1 or obtained by other methodsmay be added to a 20 mL glass vial. These organic solvent or aqueousbased ITO or ATO slurries can be coated on a number of substrates,including, but not limited to: silicon, glass, poly(ethyleneterephthalate) (PET), poly(ethylene naphthalate) (PEN), poly(imide)(PI), etc. A mold with various features described herein on it can beplaced on top of the coated ITO or ATO nanoparticle film, after themajority of the solvent has been removed and then cured using a pulsedXenon source (flash lamp), while the mold is in contact or not incontact with the nanoparticles. The photonic curing can take place invery short times, which may allow for roll-to-roll sintering ofpatterned ITO and ATO nanoparticle films to be generated at high speeds(>1 m²/s). Photonic curing allows for the thermal processing of thinfilms on relatively low temperature substrates, without damaging thesubstrate.

Having thus described several aspects of at least one embodiment of thisinvention, it is to be appreciated various alterations, modifications,and improvements will readily occur to those skilled in the art. Suchalterations, modifications, and improvements are intended to be part ofthis disclosure, and are intended to be within the spirit and scope ofthe invention. Accordingly, the foregoing description and drawings areby way of example only.

1. An optical device comprising: a patterned layer, wherein a featuresize of the patterned layer is less than or equal to 5 microns, whereinthe patterned layer comprises a composition including: a plurality ofnanoparticles, wherein a weight percentage of the plurality ofnanoparticles in the composition is greater than 70 weight percent, andwherein the plurality of nanoparticles have an average particle size ofless than 100 nm; and a binder; and wherein the patterned layer issubstantially optically transparent at least one wavelength.
 2. Theoptical device of claim 1, wherein the patterned layer is adapted tomanipulate electromagnetic radiation.
 3. The optical device of claim 1,wherein the patterned layer has an index of refraction between 1.5 and3.0.
 4. The optical device of claim 1 wherein the patterned layer is atleast 90% transparent at the at least one wavelength.
 5. The opticaldevice of claim 1, further comprising an optically transparentsubstrate, and wherein the patterned layer is disposed on the substrate.6. The optical device of claim 1, wherein the binder comprises anoptical adhesive material.
 7. The optical device of claim 1, wherein thepatterned layer includes at least one selected from columns, rows,stripes, complex shapes, irregular shapes, circles, rectangles, arcuatepatterns, and polygonal patterns.
 8. The optical device of claim 1,wherein the patterned layer includes features with an aspect ratio ofheight to width between or equal to 1.5:1 and 10:1.
 9. The opticaldevice of claim 1, wherein an RMS roughness of the patterned layer isless than 6.0 nm.
 10. The optical device of claim 1 wherein thepatterned layer is periodic.
 11. The optical device of claim 1, whereinthe average particle size is less than 40 nm.
 12. The optical device ofclaim 1, wherein the average particle size is less than 20 nm.
 13. Theoptical device of claim 1, wherein the average particle size is lessthan 10 nm.
 14. The optical device of claim 1, wherein the plurality ofnanoparticles comprise a metal oxide.
 15. The optical device of claim 1,wherein the plurality of nanoparticles comprise at least one selectedfrom zirconium oxide and titanium oxide
 16. The optical device of claim1, wherein the plurality of nanoparticles are crystalline.
 17. Theoptical device of claim 1, wherein the plurality of nanoparticles aresemi-crystalline.
 18. The optical device of claim 1, wherein theplurality of nanoparticles are amorphous.
 19. The optical device ofclaim 1, wherein the plurality of nanoparticles are crosslinked.
 20. Theoptical device of claim 1, wherein the plurality of nanoparticles havesurfaces that are unmodified.
 21. The optical device of claim 1, whereinthe composition includes ligands bound to the plurality ofnanoparticles.
 22. The optical device of claim 1, wherein thecomposition includes functional groups bound to the plurality ofnanoparticles.
 23. The optical device of claim 1, wherein the bindercomprises a sol-gel precursor material.
 24. The optical device of claim1, wherein the binder is crosslinked.
 25. The optical device of claim 1,wherein the binder material comprises at least one selected from thegroup of a monomer, oligomer, and polymer.
 26. The optical device ofclaim 1, wherein the feature size does not include a film thickness ofthe patterned layer.
 27. The optical device of claim 1, wherein thebinder comprises a precursor of a material of the nanoparticles.
 28. Theoptical device of claim 1, wherein the binder comprises at least oneselected from a metal oxide and a metal oxide precursor.
 29. The opticaldevice of claim 1, wherein the binder comprising an insulating material.30. The optical device of claim 1, wherein the binder comprises atransparent optical adhesive.